Good tidings for red tides? Responses of toxic and calcareous dinoflagellates to global change

• Main Author: Eberlein, Tim
• Other Authors: Rost, Björn, Van de Waal, Dedmer, Boersma, Maarten
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2017
• Subjects: Dinoflagellates; Phytoplankton; Climate Change; Ocean Acidification; Nutrient Limitation; 570; 570 Life sciences; biology; ddc:570; Ocean acidification
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1228; https://nbn-resolving.org/urn:nbn:de:gbv:46-00105918-19

Atmospheric CO2 partial pressure (pCO2) rises at a yet unprecedented rate, which enhances the uptake of CO2 by the surface ocean and concomitantly lowers the pH. Due to the latter, these changes are often referred to as "ocean acidification" (OA). In the last decades, consequences of OA on marine phytoplankton have been intensively studied from cellular to ecosystem level. These investigations have, however, largely focused on coccolithophores, diatoms and cyanobacteria. Little is known about the responses of dinoflagellates to OA, even though they represent an important component of phytoplankton assemblages. Moreover, owing to their type II RubisCO, a carboxylating enzyme with very low affinities for its substrate CO2, dinoflagellates may be particularly sensitive to changes in CO2 concentrations. In my first publication, I therefore investigated the impact of OA on two dinoflagellate species, the calcareous Scrippsiella trochoidea and the paralytic shellfish poisoning (PSP) toxin producing Alexandrium fundyense (previously A. tamarense). The results show that, besides species-specific differences, growth characteristics remained largely unaltered with rising pCO2 (Publication I). To understand these responses, several aspects of inorganic carbon (Ci) acquisition were investigated, revealing effective yet differently expressed carbon concentrating mechanisms (CCMs). These CCMs were moreover adjusted to the respective CO2 environment, which enabled both species to keep their growth rates relatively unaffected over a broad range of pCO2. In addition to OA, rising CO2 causes global warming, which in turn will lead to a rise in sea surface temperatures. Consequences will be an enhanced thermal stratification and a lowered nutrient resupply from nutrient-rich deep waters. Nutrient limitation may alter the response of dinoflagellates towards elevated pCO2. In Publication II, I therefore investigated the effects of rising CO2 and nitrogen (N) limitation on S. trochoidea and A. fundyense. The findings indicate a close ...